Sandvik 253 MA

Disclaimer: Recommendations are for guidance only, and the suitability of a material for a specific application can be confirmed only when we know the actual service conditions. Continuous development may necessitate changes in technical data without notice. This datasheet is only valid for Sandvik materials.

Sandvik 253 MA is an austenitic chromium-nickel steel alloyed with nitrogen and rare earth metals. The grade is characterized by:

High creep strength

Very good resistance to isothermal and, particularly, cyclic oxidation

Chemical composition (nominal) %

* To cerium should be added the quantity of other rare earth metals, since the the additive takes the form of misch metal containing about 50% Ce.

Forms of supply

Seamless tube and pipe in Sandvik 253 MA is supplied in dimensions up to 260 mm (10.2 in.) outside diameter in the solution-annealed and white-pickled condition or solution annealed by a bright-annealing process.

Other forms of supply

Fittings

Welded tube and pipe

Strip

Wire, drawn or ground

Bar steel

Plate, sheet and wide strip

Mechanical properties

Metric units, at 20°C

Proof strength

Tensile strength

Elong.

Elong.

Hardness

Rp0.2a)

Rp1.0a)

Rm

Ab)

A2"

Vickers

MPa

MPa

MPa

%

%

≥310

≥350

650-850

≥40

≥40

≈190

1 MPa = 1 N/mm2

Imperial units, at 68°F

Proof strength

Tensile strength

Elong.

Elong.

Hardness

Rp0.2a)

Rp1.0a)

Rm

Ab)

A2"

Vickers

ksi

ksi

ksi

%

%

≥45

≥51

94-123

≥40

≥40

≈190

a) Rp0.2 and Rp1.0 correspond to 0.2% offset and 1.0% offset yield strength, respectively.b) Based on L0 = 5.65 √S0 where L0 is the original gauge length and S0 the original cross-section area

At high temperatures

Metric units

Temperature

Proof strength

Tensile strength

°C

Rp.02

Rp1.0

Rm

MPa

MPa

MPa

100

≥225

≥265

≥550

200

≥189

≥215

≥475

300

≥170

≥200

≥440

400

≥160

≥190

≥425

500

≥150

≥180

≥400

600

≥140

≥165

≥340

Imperial units

Temperature

Proof strength

Tensile strength

°F

Rp.02

Rp1.0

Rm

ksi

ksi

ksi

200

≥33.5

≥39.0

≥80.5

400

≥26.0

≥31.0

≥68.5

600

≥24.5

≥28.5

≥63.6

800

≥23.0

≥27.5

≥61.0

1000

≥21.0

≥25.5

≥55.0

1200

≥19.5

≥23.0

≥46.5

Creep strength

The creep and creep rupture strength values correspond to values evaluated by the Swedish Institute for Metals Research for inclusion in the Swedish Standard. The evaluation is based on data submitted by AB Sandvik Materials Technology and Outokumpu Stainless and tests made by the Swedish Institute for Metals Research. The values apply to tube, pipe, sheet, plate and bar steel.

The higher values given in parentheses apply to Sandvik seamless tube and pipe only. The basic values have been determined by testing at intervals of 100°C and at 750°C (1380°F), under uniaxial stress and with a constant load. The mean values in the tables below have been evaluated from the test results with the aid of linear regression of the logarithmic relationship between stress and time. This evaluation has also provided the basis of interpolation and extrapolation of temperatures and times.

The temperature above which design calculations are based on creep rupture strength instead of Rp0.2 proof strength, can be read off from Fig. 1. For Sandvik 253 MA this temperature is about 550°C (1020°F). Fig. 2 shows the relationship between nominal stress and minimum creep rate, measured during testing under constant load.

Corrosion resistance

Air

Sandvik 253 MA has very high resistance to oxidation, especially at cyclically varying temperatures. See Figs. 3 and 4. The service temperature in air should not exceed about 1150°C (2100°F).

Isothermaloxidation at 1150°C (2100°F) for 100 h results in a corrosion rate of about 0.3 mm/year (13 mpy), and exposure at the same temperature for 1000 h causes about 0.2 mm/year (9 mpy).

Cyclicoxidation at 1150°C (2100oF) for 5 x 24 h, with cooling to room temperature every 24 hours gives a corrosion rate of less than 1.1 mm/year (43 mpy), which is only marginally greater than the corrosion rate at 1000°C (1830°F).

Cyclic oxidation testing for 1000 h (15 minutes at the testing temperature and 5 minutes at room temperature, making a total of 3000 cycles) places heavy demands on the elasticity and adhesive capacity of the oxide. The test results in Fig. 4 show that the resistance of Sandvik 253 MA in such difficult conditions is superior to that of both ASTM TP310 and EN 1.4828 (ASTM TP309). The very good properties of this grade in cyclic conditions have been achieved by adding rare earth metals and silicon.

Figure 4. Oxidation in air during 1000 h cyclic exposure. The cycles comprise 15 min. at the testing temperature and 5 min at room temperature. The curves represent averages.

Figure 4. Oxidation in air during 1000 h cyclic exposure. The cycles comprise 15 min. at the testing temperature and 5 min at room temperature. The curves represent averages.

Carburizing atmosphere

Carburization can occur when a material comes into contact with hot gases with high carbon activity, e.g. hydrocarbons. The degree of carburization depends on the composition of the material and on the carbon and oxygen contents of the gas.

Thanks to the relatively high chromium content and the addition of silicon and rare earth metals, a protective oxide is easily formed on the surface of Sandvik 253 MA material. Carburization resistance is, therefore, good. Fig. 5 shows carburization after 500 h at different temperatures, in a mixture of about 10% methane and about 90% argon containing 0.5% oxygen. As can be seen, Sandvik 253 MA is less prone to carburization at high temperatures in these conditions than ASTM TP310 and Alloy 800H.

In alternately oxidizing and carburizing atmospheres and carburizing slags, Sandvik 253 MA is slightly more prone to carburization than steels of higher chromium and/or nickel content.

Figure 5. Carburization of a cylindrical test piece at 0.5 mm (0.02 in.) distance from the surface after testing for 500 h at different temperatures in about 10% CH4 + about 90% Ar + 0.5% O2 .

Other gaseous atmospheres

In addition to its very good oxidation resistance in air, Sandvik 253 MA is also highly resistant to other atmospheres. The highly protective oxide layer makes it possible to use this steel at high temperatures in atmospheres containing sulphur and other aggressive compounds.

Sandvik 253 MA is more resistant than the higher alloyed 25Cr/20Ni steels to combustion gas attacks in cyclic conditions. It has an equivalent resistance, compared to the same grades, in conditions which are virtually isothermal. Sandvik 253 MA can also be used in nitrogen-containing atmospheres provided that the gas contains enough oxygen to form a protective oxide layer. In gas shields containing little or no oxygen the resistance of Sandvik 253 MA is inferior to that of Alloy 800H and 25Cr/20Ni steels as illustrated in Fig. 6. Thus, the grade is not recommended for use in muffle tubes using cracked ammonia gas.

Salt and metal melts

Compared with conventional austenitic stainless steels, Sandvik 253 MA has good resistance to cyanide melts and neutral salt melts and also to metal melts, e.g. lead, at high temperatures. Its resistance to metal melts is to a great extent determined by the oxygen content of the melt. As with other alloyed steels, corrosion is greatest at the surface of the metal bath.

Wet corrosion

Sandvik 253 MA is not generally used in conditions requiring great resistance to wet corrosion. The steel is, however, slightly more resistant than ASTM TP304 to stress corrosion cracking in chloride bearing aqueous solutions. Its resistance is more or less the same as that of ASTM TP316.

Structural stability

Because Sandvik 253 MA contains less chromium, and because of the addition of nitrogen the grade is less prone to sigma phase embrittlement than 25Cr/20Ni steels. See Fig. 7.

Heat treatment

Tubes are delivered in the heat treated condition. If another heat treatment is needed after further processing, the following is recommended:

Stress relieving

850-950°C (1560-1740°F), 10-15 minutes, cooling in air.

Solution annealing

1050-1150°C (1920-2100°F), 5-20 minutes, rapid cooling in air or water.

Welding

The weldability of Sandvik 253MA is good. Suitable methods of fusion welding are manual metal-arc welding (MMA/SMAW) and gas-shielded arc welding, with the TIG/GTAW method as first choice.

In common with all austenitic stainless steels, Sandvik 253MA has low thermal conductivity and high thermal expansion. Welding plans should therefore be carefully selected in advance, so that distortions of the welded joint are minimized. If residual stresses are a concern, solution annealing can be performed after welding.

For Sandvik 253MA, heat-input of <1.5 kJ/mm and interpass temperature of <150°C (300°F) are recommended.

Recommended filler metals

TIG/GTAW or MIG/GMAW welding

22.12.HT (e.g. Exaton 22.12.HT)

MMA/SMAW welding

22.12.HTR (e.g. Exaton 22.12.HTR)

Bending

Annealing after cold bending is not normally necessary, but this should be reviewed depending on the degree of bending and the operating conditions.

If cold bending has exceeded 10–20%, we recommend solution annealing for tubes that are to be used at temperatures above about 800°C (1450°F), and when the highest possible creep strength is required in the bent tube.

Hot bending should be carried out at 1100–850°C (2050–1560°F) and should be followed by solution annealing.

Applications

The high creep strength of Sandvik 253 MA, coupled with its excellent oxidation resistance and its good resistance to carburization in constantly carburizing gas, makes it a very suitable material for end uses in which 18/8 steels lack the necessary resistance to oxidation and carburization.

Sandvik 253 MA is often preferred instead of stainless chromium steels which have insufficient creep strength and structural stability. Furthermore, Sandvik 253 MA can very well take the place of higher alloyed materials such as 25Cr/20Ni steels and Alloy 800H, or even Alloy 600 in certain cases.

Sandvik 253 MA has come to be used extensively in the metallurgical, petrochemical and power industries. Typical applications are:

Disclaimer: Recommendations are for guidance only, and the suitability of a material for a specific application can be confirmed only when we know the actual service conditions. Continuous development may necessitate changes in technical data without notice. This datasheet is only valid for Sandvik materials.